Tunable Floating-Base Bipolar Transistor Based on 2D Material Homojunction Realized by Solid Ionic Dielectric Material
Floating-base bipolar transistors are widely used semiconductor devices because they could both amplify the signal current and suppress the noise. Employing two-dimensional (2D) materials of ultrahigh photoelectric properties could further improve the device performance. Due to the difficulty in doping, homojunction is usually not realizable for many 2D materials. Instead, a heterojunction of various 2D materials of different Fermi levels is usually needed. However, the material interface of the heterojunction deteriorates the device performance and makes the fabrication process difficult. Here, the doping difficulties have been solved by utilizing solid ionic dielectric material (LiTaO3) and a floating-base bipolar transistor based on 2D material (monolayer MoS2 here) homojunction is realized. The transistor shows tunable ambipolar transport characteristics. Particularly, under illumination, the amplification coefficient of phototransistor can be optimized by changing the gate voltage. The optimized photoresponsivity of device could reach up to 7.9 AW-1 with ultra high detectivity 3.39×1011 Jones. The overall fabrication processing is compatible to conventional processing. This design can effectively extend the application of 2D materials.